Technical Field
The present invention relates to a drilling mud composition that contains Aloe vera particles as a rheological modifier and/or a filtration control agent, and a process for fracking a geological formation using the drilling mud composition.
Description of the Related Art
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.
Drilling fluids or muds are used in the rotary drilling process of wells to tap underground collections of oil and gas. These muds have several functions. The most important functions are to assist in the removal of cuttings from the well, to seal off unwanted formations which may be encountered at different levels preventing the loss of drilling fluids to void spaces and to permeable or porous formations, to lubricate the drilling tool, to maintain the well bore pressure and stability of the bore hole, and to hold the cuttings in the suspension during events of shutdowns in drilling.
Drilling mud additives form a thin, low permeability filter cake (mud cake) over time that seals openings in formations to reduce the unwanted influx of fluids into permeable formations. A mud cake forms when the drilling fluid contains particles that are approximately the same size as or have diameters greater than about one third of the pore diameter (or the width of any opening such as induced fractures) in the formation being drilled. The drilling fluid must circulate in the wellbore (down the drill pipe and back up the annulus) to perform the above mentioned functions for the drilling process to continue smoothly. Therefore, it is essential for the drilling fluid to remain in the wellbore all the time in order to control and prevent caving of the wellbore.
Fluid loss is a common occurrence in drilling operations. As stated, drilling fluids are designed to seal porous formations intentionally while drilling, by the creation of a mud cake. However, some fluid will be lost through the mud cake and thus fluid loss control additives are required. In some situations when the borehole penetrates a fracture in the formation through which most of the drilling fluid may be lost, the rate of loss may exceed the rate of replacement. Drilling operations may have to be stopped until this zone is sealed and fluid loss to the fracture is reduced to an acceptable level. This phenomenon of losing the drilling fluid to the formation is referred to as lost circulation. Materials added to the drilling mud to stop the loss are referred to as lost circulation recovery materials or additives or simply lost circulation materials.
Loss of mud to the formation is an extremely undesirable phenomenon as it (1) leads to poor circulation and therefore less efficient removal of cuttings, (2) requires additional cost in rig time, manpower and material to replenish the lost mud and restore circulation and in extreme cases, (3) leads to insufficient downhole hydrostatic pressure which may lead to a blowout. Curing losses effectively and quickly is still a matter of concern for many companies and operators. Over the years, numerous techniques have been developed in order to cure or to reduce low to moderate loss of mud to the well bore. Under these conditions, the normal procedure is to add fluid loss agents which alone may decrease the losses while drilling to an acceptable level.
It is advantageous to maintain a lost circulation material continuously in the drilling fluid to stop the lost circulation as soon as it occurs rather than after mud flow has enlarged flow channels. The most common method in use today for the control of lost fluid circulation is the use of sealing or plugging agents in the drilling mud for bridging the pores or fissures of the sub-surface formation.
A lot of research has been conducted and documented in the literature covering natural elements used in drilling fluids. Morris G. (U.S. Pat. No. 3,042,607A—incorporated herein by reference in its entirety) disclosed the use of peach seeds as a filtration control agent using a mixture containing peach seeds with a particle size ranging from approximately a 4 mesh to 200 mesh. This size grading of the peach seeds assured that all the particle sizes necessary for the efficient bridging of the porous subsurface formations would be present in the additive. The smaller seed particles continually filter into porous formations until an effective mud sheath is formed by the larger seed particles. Lummus et al. (U.S. Pat. No. 3,629,102A—incorporated herein by reference in its entirety) used ground nutshells and nut flour as fluid loss additives and found that nutshells with a 20 to 100 mesh size and nut flour with a 100 mesh size to be the preferred particle size to avoid loss of fluid into the formation. Green, P. (U.S. Pat. No. 4,474,665A—incorporated herein by reference in its entirety) described the use of ground and sized cocoa bean shells as lost circulation material in a drilling fluid. The lost circulation controller (cocoa bean shells) had a particle size distribution ranging from 2 to 100 mesh size. Burts, B. (U.S. Pat. No. 5,118,664A; U.S. Pat. No. 5,332,724A—each incorporated herein by reference in its entirety) disclosed the use of a rice fraction and corn cob outers as lost circulation materials in drilling fluids. Creamens et al. (U.S. Pat. No. 6,630,429B1—incorporated herein by reference in its entirety) described the use of pelletized cotton seed hulls, corn starch, pelletized wood and other vegetable starch as environmentally safe lost circulation materials. Sampey, J. (U.S. Pat. No. 7,094,737B1—incorporated herein by reference in its entirety) disclosed sugar cane ash as a filtration control additive for drilling fluid applications. Ghassemzadeh, J. (U.S. Pat. No. 7,923,413B2—incorporated herein by reference in its entirety) disclosed the use of polyvinyl alcohol fibers as lost circulation materials in drilling fluids, with an average fine particle size of 5 to 15 microns, medium particles of an average size of about 20 to 150 microns and coarse particles having an average size of about 300 microns to 2500 microns.
In view of the forgoing, the objective of the present invention is to provide a drilling mud composition that contains Aloe vera particles as a rheological modifier and/or a filtration control agent, and to provide a process for fracking a geological formation using the drilling mud composition.